The present invention is directed to an optical polarizer comprising a dielectric multiple layer system which is composed of a plurality of layers having a low index of refraction alternately arranged with layers having a high index of refraction, and a pair of transparent bodies arranged on the surfaces of the dielectric multiple layer. One of the transparent bodies has a radiation entrance surface which is engaged with a medium of relatively low index of refraction for receiving incident radiation and the other of the pair of bodies has an exit surface engaged with a medium with a relatively low index of refraction for emitting radiation from the polarizer. The index of refraction of the transparent bodies, the high index of refraction layers and the low index of refraction layers are selected in such a manner that the Brewster condition is respectively met at the boundary surfaces between the layers and also between the layer system and each transparent body and also between each transparent body and the surrounding outside medium.
A polarizer, which is composed of a dielectric layer system or arrangement that has a plurality of layers and is disposed between a pair of transparent bodies such as prisms, is known as a polarizing beam divider and is disclosed in an article by Mahlein et al, Optik, Vol. 38, No. 2, 1973, pages 187-195. This device is employed as a continuously adjustable laser beam attenuator. Such a polarization beam divider is a polarization beam divider of the MacNeille type which is known and disclosed in U.S. Pat. No. 2,403,731; an article by Banning, "Practical Methods of Making and Using Multilayer Filters", Journal of the Optical Society of America, Vol. 37, No. 10, October 1947, pages 792-797 and by H. A. Macleod, Thin-Film Optical Filters, Adam Hilger Ltd., London, 1969, page 301.
A polarization beam divider such as disclosed in the article from Optik is constructed in such a manner that an alternating layer system consisting of an uneven number of m layers which alternately consist of layers having a high index of refraction n.sub.H and layers having a lower index of refraction n.sub.L in an alternate arrangement are positioned between two hypotenuse surfaces of two 90.degree. prisms which exhibit a refractive index of n.sub.G. An adhesive layer between the hypotenuse surface and the layer system should also exhibit the index of refraction n.sub.G. The index of refractions n.sub.G, n.sub.H and n.sub.L are selected in such a manner that the Brewster condition is respectively met at the boundary surfaces between the layers. Thus, a reflective power R.sub.s for radiation polarized perpendicular relative to the plane of incidence achieves a high value whereas the radiation which is polarized parallel to the plane of incidence is only weakly reflected.
In glass fiber communication technology, optical isolators, i.e., non-reciprocal optical components, are required when the optical power flux which is running backwards in the system and is caused by reflections at, for example, inhomogeneities such as joints, for example, in plugs or at splice locations, is disruptive. This is the case, for example, given laser diodes. Instabilities, which lead to increased noise and a change of the spectral emissions, occur in the laser emissions as a result of the disruptive feedback.
The optical isolators generally consist of a Faraday rotator, which is disposed between two polarizers crossed at 45.degree. to each other. Such an isolator is disclosed in an article by K. Kobayashi et al, "Microoptic Grating Multiplexers and Optical Isolators for Fiber-Optic Communications", IEEE Journal of Quantum Electronics, Vol. QE-16, No. 1, January 1980, pages 11-22. In the practical realization of such isolators, a problem is the back reflection at the input side of the polarizer which side faces the transmitter. Even the provision of good anti-blooming layers on the polarizer surface will not overcome this problem.